2006/01/07 by A. J. Williams, J. Paul Attfield, Williams, A. J. +5
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Advanced Thermoelectric Materials and Devices #FOS: Physical sciences #Physics of Superconductivity and Magnetism #Strongly Correlated Electrons (cond-mat.str-el)
paper · pdf · doi:10.48550/arxiv.cond-mat/0601131
openalex publication_date 2006/01/07 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
The structure of Na0.5CoO2, the low temperature insulator that separates the magnetic and superconducting regions in the NaxCoO2.yH2O phase diagram, is studied by high resolution powder neutron diffraction at temperatures between 10 and 300 K. Profile analysis confirms that it has an orthorhombic symmetry structure, space group Pnmm, consisting of layers of edge-sharing CoO6 octahedra in a triangular lattice, with Na ions occupying ordered positions in one-dimensional chains in the interleaving planes. The oxygen content is found to be stoichiometric within 1%, indicating that the Na concentration accurately determines the electronic doping. The Na ordering creates two distinct Co sites with different numbers of Na neighbours, but the difference in their Co-O bond distances and the derived bond valence sums is small.